Database conversion tool

[Jeff Mitchell]

Ian Monroe wrote:
> Quassel actually has a bunch of numbered .sql files, so if you have
> database version 34 and you upgrade to Quassel using database version
> 40, it'll run all the .sql files in-between. In Amarok 1.x we did have
> this sort of thing kind-of, but it'd be nice to have more of a
> standard clear way of doing it.

But it was located in the increasingly-messy collectiondb.cpp, had to be 
compiled every time a change was made, etc.  I like the idea of numbered 
.sql files containing statements that could simply be executed (this 
also follows the path of many other applications which keep database 
modification statements external).

--Jeff